Introduction to Health Physics: Fourth Edition - Ruang Baca FMIPA UB

632 CHAPTER 11
The experiment is to be done in a laboratory of dimensions 15 ft × 10 ft × 8 ft.
The laboratory is ventilated at a rate of 100 ft 3 /min.
(a) Do any special measures have to be taken in order to control the atmospheric
concentration of the 36Cl to 10% of its DAC (DAC = 1 × 10−6 μCi/cm3 )?
(b) To what concentration of chloroform, in parts per million, does the radiological
DAC correspond for this compound? Compare this concentration to
the chemical PEL for chloroform.
11.7. For the purpose of estimating hazards from toxic vapors or gases of high molecular
weight, it is sometimes incorrectly assumed that settling of the vapor is determined
by the specific gravity of the pure vapor, which is defined as
Molecular weight of the pure vapor
“Molecular weight” of air
instead of the correct specific gravity given by
“Molecular weight” of air and vapor mixture
.
“Molecular weight” of air
(a) If the vapor pressure of benzene (benzol), C6H6, is 160 mm Hg at 20◦C, calculate the correct specific gravity of a saturated air mixture of benzene
vapors and compare it to the specific gravity of the pure vapor.
(b) If the chemical PEL for benzene is 10 ppm by volume, calculate the specific
gravity of an air–benzene mixture of this concentration.
(c) What is the maximum specific activity of 14C-tagged benzene in order that
one-half the radiological DAC for 14C (DAC = 1 × 10−6 μCi/cm3 ) not be
exceeded by a benzene concentration of 10 ppm?
11.8. Iodine-131 is to be continuously released to the environment through a chimney
whose effective height is 100 m and whose discharge rate is 100 m3 /min. The
average wind speed is 2 m/s and the lapse rate is stable.
(a) At what maximum rate may the radioiodine be discharged if the maximum
downwind ground level concentration is not to exceed 10% of the 10 CFR
20 DAC of 2 × 10−8 μCi/cm3 (700 Bq/m3 ).
(b) How far from the chimney will this maximum occur?
11.9. Inhalation exposure is often described as the product of atmospheric concentration
and time, as in units of Bq-s/m3 . Using the ICRP assumptions that 23%
of inhaled iodine is deposited in the thyroid, and that the thyroid weighs 20 g,
calculate the dose to the thyroid due to an acute exposure of 1 Bq-s/m3 of
(a) 131I. (b) 133I. (c) Assuming that the other 77% of the inhaled iodine is absorbed into the
blood and is bound to the protein, calculate the total body doses due to the
protein-bound iodine.
(d) What is the effective dose from each isotope?
11.10. Disposal of animal carcasses in a biomedical research institution is by incineration.
If the incinerator consumes air at the rate of 34 kg/min, how much 131I